Contrary to what a few people have said here, my NCT anti natal classes should have had the subheading "...when good births go bad!" - passing round photos of babies with badly bruised cone heads, how to spot a prolapsed cord when your waters break, induction, in depth discussion on drugs, pain relief, forceps, ventrouse and emcs. Not one mention of my rights to question or refuse treatment or drugs to me or my baby, it was a "this is what's going to happen to you when it all hits the fan" class.
During the NCT breast feeding class she talked about problems some women have with breast feeding, different ways to can get help but also loads of info on bottle feeding, how much an frequently to feed, steralising bottles etc.
Don't presume that they'll be pushing some sort of barefoot Mother Earth, anti-medical angle on you. In my experience it was very far from that.
I'm sure some people found them helpful but I didn't particularly. Instead of the NCT classes I'd strongly recommend reading the AIMS books to inform yourself with the basic facts and your rights, then one of the trillion "what to expect" books on the market (and Mumsnet) for understanding what's happening to your body, and then join a baby group, baby massage, baby swimming, breast feeding cafe etc to meet other local mums.